Antique sponge.
An example of the element Palladium

Back in the early 20th century, we did not have the monolithic and ubiquitous chemical companies like the Alfa Aesars and Sigma Aldriches we see today, industrial powerhouses manufacturing specialized chemicals for research and laboratories. So, if a professor needed a metal or chemical such as this in a small amount, he (always a he back then) would either have to produce it at the university or laboratory where he was working, or appeal for some samples from a personal contact working one of the few companies dealing with uncommon materials, in this case, precious metals.

Palladium is used as a catalyst where surface area is important, so it may have been produced in sponge form for this reason, but it is more likely that this is the raw palladium directly after it was produced. Most of the laboratory-scale reductions of palladium from one of its compounds and even some variations of the industrial ore refining and isolation process give sponge-type metal, which is then either remelted into a larger ingot or powdered further.